Article

Effects of Different Organic Acids in Iron Removal from Kaolin Ore

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Abstract

To reduce the iron content of kaolin to the desired levels, a variety of industrial physical and chemical processes are employed in practice. Though the physical methods (classical magnetic separation, new and more expensive super conductive magnetic separation in particular) are extensively used, generally low efficiency of these methods has led to the search for alternative chemical methods for the removal of iron, which have gained importance recently. In this study, the chemical removal of the iron impurity present in kaolin supplied by ÇİMSA Inc. was investigated by using organic acids. The effect of parameters including the type of organic acids, temperature, pulp density, leaching time and reagent concentration on the extent of iron removal were investigated applying factorial design ANOVA-Yates test technique for the statistical analysis of the results. Under optimum condition (10% pulp ratio, 40 g/L of oxalic acid concentration, 90°C temperature and 120 minutes of leaching (reaction) time), the removal of Fe2O3 was obtained as 34.45% for oxalic acid leaching.

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... Ambikadevi and Lalithambika (2000) evaluated the effectiveness of several organic acids (acetic, formic, citric, ascorbic acids etc.) to dissolve iron from iron compounds. Oxalic acid was most promising because of its acid strength, good complexing characteristics and high reducing power, compared to other organic acids (Nwoye et al., 2009;Tuncuk et al., 2010). ...
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Leaching studies of low-grade Joda manganese ore containing 24.7% Mn and 28.4% Fe were carried out at high temperature and atmospheric pressure using oxalic acid as reductant in sulphuric acid medium. The experiments were designed according to 24 full factorial design, and regression equations for extraction of manganese, iron and aluminum were determined from the data. All the significant main and interaction effects on extraction of Mn, Fe and Al have positive effect, except oxalic acid concentration and time interaction for extraction of Al. Oxalic acid concentration has strongest effect on extraction of Mn, whereas temperature and time have strongest effect on extraction of Fe and Al, respectively. 98.4% Mn and 8.7% Fe were extracted from −150+105 μm ore with 30.6 g/l oxalic acid, 0.543 M sulphuric acid concentration at 85 °C in 105 min.
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The light-induced dissolution of the iron oxide, lepidocrocite (γ-FeOOH), has been investigated and found to be greatly enhanced in the presence of citrate. A conceptual model of the dissolution process is presented and validated through studies of citrate adsorption to lepidocrocite, net iron oxide dissolution under a variety of conditions, and solution phase redox reactions. The initial dissolution rate is directly related to the concentration of the surface bound ferric citrate and the first order rate constant for the photodissolution process is very similar to that found for the photodissociation of soluble ferric citrate. Dissolution most likely occurs through direct excitation of charge transfer bands of the surface bound ferric citrate. At low pH (pH 4.0), a constant rate of dissolution is observed while at higher pH (pH 6.5 and 8.2), the dissolution rate decreases on continued photolysis. This decrease is due to (1) an oxygen-dependent deactivation process occurring at the surface and (2) loss of photo-produced iron from solution by “ligand-like” adsorption of soluble iron citrate complexes by the colloidal iron oxide. Superimposed on the dissolution process at these higher pH is a rapid oxidation-reduction cycle involving solution phase iron species with the reduction step induced by photodissociation of ferric citrate complexes and the oxidation step controlled by the formation of ferrous citrate.
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We report a novel protocol to prepare titania hollow nanospheres of size about 28 ± 1 nm with micelles of asymmetric triblock copolymers. The hollow particles exhibit unique electrochemical properties in lithium ion rechargeable batteries such as high capacity, very low irreversible capacity loss, and high cycling performance.
Article
Low- and high-defect kaolinites mechanochemically activated for different periods of time have been treated with sulfuric acid solution. These modified materials were analyzed using a combination of X-ray diffraction, thermogravimetry, chemical analysis, diffuse reflectance Fourier transform infrared spectroscopy, as well as specific surface area and pore size distribution measurements. In addition to the mechanochemically amorphized part, the disordered and the adequately distorted phases also reacted with sulfuric acid. The specific surface areas of the leached samples of the partially or the completely amorphized materials were found to be greater than those of the thermally amorphized ones. The acid treatment results in a greater total pore volume for the partially amorphized materials than for the totally amorphized mineral. The partially amorphized high-defect kaolinite was proved to be more soluble than the low-defect kaolinite under similar conditions.
a (108M180 no'lu proje) teşekkür ederiz. Ayrıca cevherlerin temininde yardımları ve destekleri için ÇİMSA A.Ş. yetkililerine, deneysel çalışmalarında teknik desteklerinden dolayı SDÜ Jeotermal Enerji
  • Teşekkür Desteklerinden Dolayı
TEŞEKKÜR Desteklerinden dolayı TÜBİTAK'a (108M180 no'lu proje) teşekkür ederiz. Ayrıca cevherlerin temininde yardımları ve destekleri için ÇİMSA A.Ş. yetkililerine, deneysel çalışmalarında teknik desteklerinden dolayı SDÜ Jeotermal Enerji, Yeraltısuyu ve Mineral Kaynakları Araştırma ve Uygulama Merkezi personeline ve mineralojik analizlerdeki yardımlarından dolayı Yrd. Doç.
Şemsettin Caran'a, deneysel çalışmalardaki yardımları için Müh
  • Dr
Dr. Şemsettin Caran'a, deneysel çalışmalardaki yardımları için Müh. Mustafa Şahin ve Müh.
Kaolenlerin Safsızlaştırılmasında Kimyasal ve Biyolojik Yöntemlerin İncelenmesi
  • Kaynaklar Akçıl
  • A Tuncuk
KAYNAKLAR Akçıl, A. ve Tuncuk, A., 2006; " Kaolenlerin Safsızlaştırılmasında Kimyasal ve Biyolojik Yöntemlerin İncelenmesi ", Kil Bilimi ve Teknolojisi Dergisi, 1, 59-69.
Biyoliç Yöntemiyle Endüstriyel Hammaddelerden Safsızlıkların Uzaklaştırılmasının Araştırılması
  • V İ Arslan
Arslan, V.İ., 2008; " Biyoliç Yöntemiyle Endüstriyel Hammaddelerden Safsızlıkların Uzaklaştırılmasının Araştırılması ", (Doktora Tezi), Çukurova Üniversitesi Fen Bilimleri Enstitüsü.
Purified Quartz and Process for Purifying Quartz " , United States Patent
  • K B Loritsch
  • R D James
Loritsch, K.B. ve James, R.D., 1991; " Purified Quartz and Process for Purifying Quartz ", United States Patent, Patent Number : 4,983,370.
Introduction to Probability and Statistics Principles and Applications for Engineering and The Computing Sciences Design and Analysis of Experiments Teknolojik ve Bilimsel Araştırmalarda Modern Deney Tasarımcılığı ve Optimizasyon Yöntemleri
  • J S Milton
  • J C Arnold
Milton, J.S. ve Arnold, J.C., 1995; " Introduction to Probability and Statistics Principles and Applications for Engineering and The Computing Sciences ", Factorial Experiments, 14, 604-655. MINITAB 15, 2009; Statistical Software. Montgomery, D.C., 1991; " Design and Analysis of Experiments ", 3rd ed., Wiley, New York. Özensoy, E., 1982; " Teknolojik ve Bilimsel Araştırmalarda Modern Deney Tasarımcılığı ve Optimizasyon Yöntemleri ", M.T.A. Enstitüsü Yayınları Eğitim Serisi, 24, 26-35.
The Role of Bacterial Alteration in Whitening and Iron Removal from Georgia's Commercial Kaolin Clays
  • E Shelobolina
  • S M Pickering
  • J E Kogel
Shelobolina, E., Pickering, S.M. ve Kogel, J.E., 2002; " The Role of Bacterial Alteration in Whitening and Iron Removal from Georgia's Commercial Kaolin Clays ", SME Annual Meeting, Phoenix, Arizona.
The Economics of Kaolin
  • Roskill
Roskill, 2006. The Economics of Kaolin, 12th ed. Roskill Information Services, Ltd.
Industrial minerals in Arizona's paint industry. Open-file Report. Arizona Department of Mines and Mineral Resources
  • K A Philips
Philips, K.A., 1989. Industrial minerals in Arizona's paint industry. Open-file Report. Arizona Department of Mines and Mineral Resources, pp. 1-8.
Teknolojik ve Bilimsel Araştırmalarda Modern Deney Tasarımcılığı ve Optimizasyon Yöntemleri
  • E Özensoy
Özensoy, E., 1982; " Teknolojik ve Bilimsel Araştırmalarda Modern Deney Tasarımcılığı ve Optimizasyon Yöntemleri ", M.T.A. Enstitüsü Yayınları Eğitim Serisi, 24, 26-35.
Spectroscopic control of iron oxide dissolution in two ferralitic soils
  • N Malengreau
  • A Bedidi
  • J P Muller
  • A J Herbillions
Malengreau, N., Bedidi, A., Muller, J.P., Herbillions, A.J., 1996. Spectroscopic control of iron oxide dissolution in two ferralitic soils. Eur. J. Soil Sci. 47, 13-20.
Processo per la rimozione del ferro da concentrati di caolino. Quarzo ed altri minerali di interesse industriale
  • L Toro
  • B Paponetti
  • A Marabini
  • B Passariello
Toro, L., Paponetti, B., Marabini, A., Passariello, B., 1990. Processo per la rimozione del ferro da concentrati di caolino. Quarzo ed altri minerali di interesse industriale. Italian Patent Nr. 21707A/90.